Plaster board and the like



Patented Dec. 4,1928,

UNITED STATES PATENT oF ncE.

WILLIAM HOFFMAN KOBBE, OF 1\TEW YORK, 1\'|'. Y., ASSIGNOB TO TEXAS GULF SUI- PHUR COMPANY, OF BAY CITY, TEXAS, ACORPORATION OF TEXAS.

vrnns'rnn BOARD AND 'rnnmrxn.

No Drawing.

This invention relates to articles made of hardened plaster and coveredin part at least with fibrousmaterial, such as plaster board and the like. The invention contemplates certain improvements in the manufacture of such articles. as well as a new and improved treated with molten sulfur in an attempt to article of this character.

The ordinary plaster boards of commerce are made up of a body of hardened plaster, usually gypsum plaster,. covered in Whole or in part with fibrous material. usually a wood pulp paper. In accordance with my present invention the fibrous covering of plaster board and similar products is'impregnated to a desired extent with sulfur, and preferably the sulfur impregnation is conducted so as to strengthen the bond --between the plaster body and its fibrous covering by congealed sulfur. The impregnation of the fibrous covering may advantageously be effected by immersing the plaster board or similar article in a bath of molten sulfur and subsequently permitting the molten sulfur to congeal in the interstices of the fibrous material. L

The body or interior of plaster board is ordinarily hardened gypsum plaster. Byl gypsum I mean calcium sulfate, with or without water of crystallization, plaster of Paris,

anhydri'te, albaster and all natural and conimercial forms of these substances. Gypsum usually occurs with two molecules of water of crystallization (CaSO -2H O) and is calcined until the water of crystallization is reducedto one-half molecule (CaSO -1/2H O) or until all of the water of crystallization has V been driven off. After calcining and grinding the gypsum is mixed with water which causes it to set or harden. Although the exact chemical changes which take place are obscure, it is probable that the gypsum reverts to its native or initial state with two molecules of water of crystallization. How} ever this maybe, so far as the present in- 'vention is concerned it is applicable to all forms of set or hardened gypsum plaster regardless of the water content.

Various 'commereial forms of gypsum or plaster board may be employed in'the practice of the invention, such, for example, as rock lath, sheet rock, gyp lap, Sackett board, etc. It is to be understood, however, that v the invention is not limited to these products,

but may be advantageously applied to any article made up ofa hardened plaster body Application filed March 14, 1927. Serial No. 175,432.

impregnate it, but I find that certain difficulties are encountered. The lowest temperature at which sulfur may be used is above the calcining temperature of gypsum and therefore the water of crystallization is driven off and themass of gypsum becomes wholly or in part calcined and weakened. For this reason efforts have been made to modify the melting point of sulfur which'is a difficult and impractical thing to accomplish, and attempts have been made to inject sulfur into the gypsum by means of a solvent which is likewise extremely difficult and which, if accomplished, would give very different results from using molten sulfur as a saturating medium.

I have discovered that a sheet of setoor hardened gypsum or similar plaster product which is held togetherand bound with a uniform covering material such as fibre board, may be readily impregnated by immersion in a bath of molten sulfur at 120- to 140 C. without any deleterious results and a preferred embodiment of the process may be described as follows: Sheets of rock lath, for example, of any appropriate thickness, are cut to size and immersed in a bath of molten sulfur at 120 to 140 C. either in a horizontal or vertical position until the fibre covering has become fully saturated with the molten sulfur to-.

gether with the'surface of the gypsum that is in immediate contact with this fibre cover- 'ing. This is accomplished in one or two hours or even less, depending upon the thickness 'Upo'n removal from the treating bath the molten sulfur is held within the fibre covering a and in the gypsum immediately adjacent thereto by capillarity and this sulfur, due to its low latent heat, very quickly solidifies especially if placed in a current of air or otherwis'echilled and the loss from exudation or dripping is negligible.

These treated fibre gypsum products if not i I perfectly flat may be pressed while still hot fectly true and flat product assured. As aclose rule, however, the products mentioned are generally'flat and this is unnecessary. On the other hand, they may be deliberately curved or otherwise shaped to a slight degree if this is desirable, but it is importantto manipulate them while the sulfur is either molten or in its transition stage as one of the great advantages of the treatment is the fixation which is brought about by stable, rhombic crystals of sulfur.

In my co-pending patent applications, Serial No. 61,831, filed October 10, 1925, and Serial No. 124,784, filed July 24, 1926, methods are described for coloring sulfur and for coloring various materials with colored sulfur and I find that the processes there described are applicable in the practice of the present invention. In acordance with the methods there described, I may include in the practice of the present invention sulfur soluble dyes with the sulfur and thereby impart attractive shades of color ,to these fiber gypsum products, and I find that the color penetrates as far as the sulfur itself, and is of a highly permanent nature. I

Products made in accordance with the invention have numerous practical commercial advantages. Set gypsum, in itself, or the various products composed in part of set gypsum, is not proof against weather or moisture I and consequently cannot be used out of-doors. These products arehydroscopic and rapidly disintegrate when exposed to moisture and are readily acted" upon by various acids and chemical fumes. They also lack physical strength for many purposes.

Plaster board and similar products when treated in accordance with the method of the invention are proof against all normal. weather conditions and satisfactorily withstand various acids and chemical fumes. The sulfur saturated fibrous covering, regardless of the degree of penetration of the sulfur into the psum itself, entirely protects the en- ?gypsum from any destructive influences, in addition to greatly increasing its strength. By partially impregnating the gypsum as well as the fibrous container or covering, these qualities are enhanced and a product results which is waterproof and acid Q resistant to a high degree.

multitude (if other products.

The new plaster board product of the in-.

- vention may be painted, varnished, laquered or shellacked, and will take practically any finish, or it may be colored as hereinbefore described and given a high finish by sanding,

bufiing polishing. In many cases in order to reduce flammability, it is desirable to give the impregnated article a finishing coat of paint or lacquer. These highly finished materials are suited for radio panels, wall tile and various sanitar products such as parts for partitions, baseboards and as a general substitute for slate and other slab materials.

While I have mentioned various commercial forms of gypsum or plaster board, I do not wish to confine'myself to these products",

since the invention is not limited to these particular products, but is applicable to any form of hardened plaster or gypsum which is covered in whole or in part by fibrous material. The impregnation with sulfur of such prod- ,ucts or articles will principally extend to the fibrous material and will generally only afiect the plaster which is immediately adjacent to the fibrous material, thereby, however, strengthening the bond between the plaster and its fibrous covering.

I claim:

1. A, composition board comprising an interior including hardened plaster covered in part at least by fibrous material, the fibrous material being bonded to the interior of the board by crystals of sulfur.

' 2. An article of manufacture comprising an interior including hardened plaster covered in part at least by a sulfur impregnated fibrous material, said impregnated material being bonded to the interior of the board by crystals of sulfur.

In testimony whereof I aflix my signature.

WILLIAM HOFFMAN KOBBE. 

